Why do 'they' want to control guns? 1. 'They' need to justify their existence. 2. 'They' have no other easier target of opportunity.
Further, addressing correlations and symptoms is always easier and more convenient than addressing cause/effect or the real problem. Besides, with correlations and symptoms you can always declare 'vicotry', which is generally hard to refute, and that makes for good photo ops and sound bites.
Additionally, controlling inanimate objects tends to be easier than sentient beings with will.